Molybdenum plays an essential role in the metalloenzyme, nitrogenase, the dinitrogen-fixing systems of microorganisms. Although there is no direct evidence as to the nature of the molybdenum-binding site, the accumulating data suggests a dimeric site with cysteine sulfur coordination. The major objective of the proposed research is to provide new chemical and structural information about molybdenum-sulfur complexes. Synthetic efforts have been directed toward the preparation of sulfido and oxo-bridged molybdenum dimers, as synthetic analogues for possible metal binding sites in the nitrogenase enzyme. A series of asymmetric mixed ligand dimers of general formula Mo2O(LL)2(LL')2, where LL equals -S2CSR or -S2CNR2 and LL' equals PhCSN2, H2NCSNHNCR2 or RSCSNHNR2, will also be investigated in an effort to elucidate the importance of metal-metal bonding in complexes of this type. Chelating sulfur ligands will be investigated in an effort to define structural trends. The molecular structure and electro-chemical behavior of the complexes will be studied with a view to providing structure-function correlations of possible relevance to the nitrogenase enzyme system.